Download - 125 GeV Higgs at the LHC: h ZZ , WW
125 GeV Higgs at the LHC: hZZ, WW
Susumu Oda (Kyushu University) On behalf of the ATLAS and CMS Collaborations
Higgs and Beyond 2013Tohoku University, 2013-06-05
1/28
Production and decay of the SM Higgs boson
(ggF) (ttH)
(VH) (VBF)
Ferm
ioni
cBo
soni
c2/28
• A new boson with a mass of about 125 GeV was observed in the Standard Model Higgs boson searches by ATLAS and CMS in 2012.
• Gluon-gluon fusion process is the dominant production mode. • I will focus on the two decay modes with the highest sensitivities.• ZZ(*)4l decay mode provides the cleanest final state with the full
reconstruction of the mass of the new boson. – The statistics are limited.
• WW(*)lnln decay mode provides a large branching ratio and a relatively clean final state. – Limited mass resolution due to missing ET by undetected neutrinos
hZZ(*)4l: event display
Four isolated high-pT leptons (two same-flavor opposite-sign lepton pairs)
m4l=127.4 GeV
Invariant mass of the 4-lepton system, m4l, is the final discriminating variables.
3/28
hZZ(*)4l: selections (1/3)
CMS• Electrons
– pT>7 GeV– |h|<2.5 – Multivariate based identification
• Muons– pT>5 GeV– |h|<2.5
• Taus– Used for high mass Higgs search
ATLAS• Electrons
– pT>7 GeV– |h|<2.47 – Cut based identification
• Muons– pT>6 GeV– |h|<2.7
• Taus– Not used
• 4 final states at low mass Higgs search: 4e, 2e2m, 2m2e, 4m • In the 2e2m/2m2e case, pairs ordered respect to mass.
High mass ZZ1, m12=mZ1
Low mass Z(*)
Z2, m34=mZ2(*)
4/28
CMS• Isolation cut
– Normalized by the lepton pT
– Sum of pT of charged tracks and neutral particles in DR=0.4
– Selection cut is <0.4• Impact parameter cut
– IP significance (3D) <4s
• Final State Radiation correction– All leptons– Photons
• 2<ET<4 GeV, DR<0.07• ET>4 GeV, 0.07<DR<0.5 • Normalized isolation<0.1
– Efficiency: 50%– Purity: 80%
hZZ(*)4l: selections (2/3)ATLAS• Isolation cuts
– Normalized by the lepton pT– Track isolation (DR=0.2)<0.15– Calorimeter isolation (DR=0.2)<0.2 (0.3) for
electrons (muons)• Impact parameter cut
– IP significance (2D) <6.5s (3.5s) for electrons (muons)
• Final State Radiation correction– Only for Z1mm,
• 66<m12<89 GeV and mmmg<100 GeV– Photons
• ET<3.5 GeV, DR<0.08• ET>3.5 GeV, DR<0.15
– Efficiency: 70%– Purity: 85%
5/28
hZZ(*)4l: selections (3/3)ATLAS• Quadruplet
– pT>20, 15, 10, 7 GeV• >6 GeV if the 4th lepton is a
muon– m12=[50, 106] GeV
– m34=[12*, 115] GeV• *Lower cut increases for
m4l>140 GeV• Jets
– Anti-kT DR=0.4
– pT>25 (30) GeV for |h|<2.5 (2.5<|h|<4.5)
• Integrated luminosity– 4.6 fb-1 at Ös=7 TeV– 20.7 fb-1 at Ös=8 TeV
CMS• Quadruplet
– pT>20, 10, 7, 7 GeV• >5 GeV if the 3rd or 4th
lepton is a muon– m12=[40, 120] GeV
– m34=[12, 120] GeV
• Jets– Anti-kT DR=0.5
– pT>30 GeV, |h|<4.7
• Integrated luminosity– 5.1 fb-1 at Ös=7 TeV– 19.6 fb-1 at Ös=8 TeV
ATLAS and CMS use similar selections and amount of data .
6/28
hZZ(*)4l: signal mass resolution
ATLAS
CMS
4e 2e2m/2m2e 4ms=2.4 GeV s=1.9 GeV s=1.6 GeV
s=2.0 GeV s=1.7 GeV s=1.2 GeV
Single Gaussianfunctionwith the Z mass
constraint on Z1
Double-sided
Crystal-Ball
function
CMS has slightly better resolution than ATLAS mainly due to better calorimeter energy resolution and stronger solenoid B-field (3.8 T vs 2.0 T).
7/28
hZZ(*)4l: event categorization
• In Category I, pT/m4l is used to discriminate VBF and VH from ggF. • In Category II, a linear discriminant (VD) is formed by combining
two VBF sensitive variables, the difference in h (Dhjj) and the invariant mass of the two leading jets (mjj).
ATLAS• There are at least two jets. • The 1st and 2nd highest pT jets are separated by >3 in h and have the invariant mass of >350 GeV.
• There is at least one lepton with pT>8 GeV.
yes
yes
no
VBF-like category
VH-like category
ggF-like category
There are jets in the forward and backward regions.
There is at least one lepton from a W or Z bosonOthers
no
CMSyes
Category II
Category I
no• There are at least two jets.
About 20% signal from VBFAbout 5% signal from VBF
8/28
hZZ(*)4l: backgrounds• ZZ(*) di-boson production: irreducible background
– Estimated using MC simulation normalized to the theoretical cross section.
• Z+jets, ttbar: reducible background– Estimated with data-driven methods with Z+ll and Z+l
control regions • Increase the statistics by loosening or inverting the
selections of additional lepton(s) • Estimate background composition• Extrapolate the background composition to the signal
region based on simulation
KD
• CMS uses a kinematic discriminant (KD) to reject the irreducible ZZ(*) background. • KD is based on the probability ratio of the signal and
background hypotheses. • Leading-order matrix elements define the probabilities.
9/28
hZZ(*)4l: expected and observed eventsATLAS (100-160 GeV) at 8 TeV 4e 2e2m/2m2e 4mZZ(*) 5.4 +/- 0.5 14.7 +/- 0.9 12.4 +/- 0.6Z, Zbbbar, ttbar 2.5 +/- 0.6 6.1 +/- 1.5 1.9 +/- 0.6Total background 8.0 +/- 0.8 20.8 +/- 1.8 14.3 +/- 0.8Signal mH=125 GeV 2.9 +/- 0.4 7.0 +/- 0.9 5.8 +/- 0.7Data 13 28 27
CMS (110-160 GeV) at 7 TeV and 8 TeV 4e 2e2m/2m2e 4mZZ(*) 6.6 +/- 0.8 18.1 +/- 1.3 13.8 +/- 1.0Z+X 2.5 +/- 1.0 4.0 +/- 1.6 1.6 +/- 0.6Total background 9.1 +/- 1.3 22.0 +/- 2.0 15.4 +/- 1.2Signal mH=125 GeV 3.5 +/- 0.5 8.9 +/- 1.0 6.8 +/- 0.8Data 16 32 23
Although this is not direct comparison, ATLAS and CMS seem to have similar signal acceptance and S/N ratio.
10/28
hZZ(*)4l: m4l distributions• A clear peak exceeding expected backgrounds is seen around
m4l=125 GeV by both ATLAS and CMS.• Single resonant Z4l peak is seen at right position and height.
ATLAS CMS
11/28
hZZ(*)4l: m12 and m34 distributions
• Data agree with the expected distributions.
ATLAS (120<m4l<130 GeV) CMS (121.5<m4l<130.5 GeV)
m12=MZ1
m34=MZ2
12/28
hZZ(*)4l: mass of the Higgs-like boson, mH
ATLAS CMS
• ATLAS: 1D fit to m4l
• CMS: 3D fit to m4l, event-by-event uncertainty (dm), KD
• The systematic uncertainty is dominated by electron energy and muon momentum scale systematic uncertainties.
GeV (syst)(stat)3.124 5.03.0
6.05.0
Hm
GeV 0.2(syst)(stat)5.08.125 Hm
13/28
hZZ(*)4l: significance
ATLAS CMS
• ATLAS: 1D fit to m4l
– 6.6s observed (4.4s expected) at mH=124.3 GeV
• CMS: 3D fit to m4l, KD, pT/m4l or VD
– 6.7s observed (7.2s expected) at mH=125.8 GeV• 1D (m4l) fit gives 4.7s observed (5.6s expected) at mH=125.8 GeV
– 3D fit of CMS largely improves statistical significance.
14/28
hZZ(*)4l: signal strength (=sobs/sSM)ATLAS
Inclusive m Fermionic mF Bosonic mV Ratio mV/mF
ATLAS at mH=124.3 GeV
1.7+0.5-0.4 1.8+0.8
-0.5 1.2+3.8-1.4 0.7+2.4
-0.3
CMS at mH=125.8 GeV
0.91+0.30-0.24 0.9+0.5
-0.4 1.0+2.4-2.3 -
CMS
One VBF-like event at 123.5 GeV observed 0.71 +/- 0.10 event expected (~0.4 event from VBF)
No VBF-like (VD>0.5) events observed in Category II
• All signal strengths are consistent with 1 (=the SM expectation) within 2s uncertainties.
• Used masses are different and results cannot be directly compared.
15/28
hZZ(*)4l: spin and parity• Several JP hypotheses are tested against the JP=0+ hypothesis (=Standard Model
Higgs) with Matrix Element Likelihood Approach and Boosted Decision Tree. • Data strongly favor JP=0+.
JP BDT CLs JP-MELA CLs
0- 2.2% 0.4%1+ 0.2% 0.6%1- 6.0% 3.1%
2+m 16.8% 18.2%
2- 25.8% 11.6%
JP JP-MELA CLs
0- 0.16%0+
h 8.1%1+ <0.1%1- <0.1%
2+mgg 1.5%
2+mqq <0.1%
ATLAS
CMS
16/28
hWW(*)lnln: event displays
Two isolated high-pT leptons with opposite charges with small opening angle and large missing transverse energy (+ two forward jets in VBF production)
17/28
hWW(*)lnln: selections (1/2)
CMS• Events with >=2 jets are not
considered. • Lepton pT thresholds
– 23, 10 GeV• mll cuts
– mll>12 GeV– mll<43 GeV
• Dfll<1.75 radian (=100 degrees) cut• pTll>30 GeV
ATLAS• Events with >=2 jets are considered
for the VBF analysis. • Lepton pT thresholds
– 25, 15 GeV• mll cuts
– mll>10 GeV (DF), >12 GeV (SF)– mll<50 GeV (Njet=0, 1), <60 GeV
(Njet>=2)• Dfll<1.8 radian cut• pTll>30 GeV only for Njet=0
• Vectors from the decay of a scalar particle and the V-A structure of the W boson decay lead to a small opening angle. • Different flavor (DF: em, me) and same flavor (SF: ee, mm) • Discriminating variables: pTll, mll, Dfll, mT
18/28
hWW(*)lnln: selections (2/2) CMS• Ztt veto is not used. • Missing ET, charged track MET
(=MpT)– Relative to leptons– Track MET in all channels– MET rel>20 GeV– MpT rel>20 GeV
• mT cuts– 80 < mT < 123 GeV
ATLAS• Ztt veto for Njet=1, >=2• Missing ET, charged track MET
(=MpT) – Relative to leptons and jets– Track MET only in same flavor
channels– MET rel>25 GeV (different
flavor), >45 GeV (same flavor)– MpT rel>45 GeV (same flavor)
• mT cuts– 93.75 < mT < 125 GeV for Njet=<1– mT<150 GeV for Njet>=2
,
cos12 missTE
missTTT Epm fD
missT
missrelT
closestmissT
missrelTclosest
EE
EE
DD
,
,
Else,
sin ,2
If ff
22
22 missTT
missTTT Emm Epp
19/28
hWW(*)lnln: backgrounds• Where feasible, background contributions are estimated directly from data or
normalized to the observed rate in a data control region. • Non-resonant WW(*) di-boson production
– More uniform opening angle (small opening angle by HWW(*)lnln)– ATLAS: estimated with control region is 50<mll<100 GeV (Njet=0), mll>80 GeV (Njet=1)
– CMS: estimated with control region is mll>100 GeV
• Top quark production– ATLAS: suppressed by b-jet veto with nominal threshold (ET>25 GeV)
– CMS: suppressed by b-jet veto with sub-threshold (ET>15 GeV), soft muon veto
• Drell-Yan process (Z/g*) in same flavor– ATLAS: Tight MET/MpT, frecoil (a measurement
of soft hadronic recoil opposite to dilepton (dilepton+jet) system in Njet=0 (Njet=1))• Rejection ~2-4 with efficiency ~70%
– CMS: A dedicated multivariate selection with MET, kinematic and topological variables. • Rejection ~1000 with efficiency >50%
20/28
hWW(*)lnln: signal extraction• ATLAS
– Split em+me at mll=30 GeV for Njet=0 and 1
– The full mT distribution is divided into 5, 3 and 4 bins for Njet=0, 1 and >=2, respectively.
– Fit mT distribution to extract signal strength, m. • CMS
– Cut-based analysis – 2D shape-based analysis with mT and mll is
used for different flavor.
SR1: 10<mll<30 GeVSR2: 30<mll<50 GeVWW CR: 50<mll<100 GeV
21/28
hWW(*)lnln: expected and observed eventsATLAS (8TeV) Nobs Nsig Nbkg NWW Nttbar NZ/g*
Njet=0 831 97 +/- 20 739 +/- 39 551 +/- 41 23 +/- 3 30 +/- 10
Njet=1 309 40 +/- 13 261 +/- 28 108 +/- 40 68 +/- 18 12 +/- 6
Njet>=2 55 10.6 +/- 1.4 36 +/- 4 4.1 +/- 1.5 4.6 +/- 1.7 22 +/- 3
CMS (8TeV) Nobs Nsig Nbkg NWW Ntop NWZ,ZZ,Z/g*
Njet=0 em+me 505 90 +/- 19 429 +/- 34 310 +/- 29 20.0 +/- 4.3 11.4 +/- 1.1
Njet=0 ee+mm 421 56 +/- 12 360 +/- 38 207 +/- 19 9.3 +/- 2.2 106 +/- 31
Njet=1 em+me 228 42 +/- 12 209 +/- 14 80 +/- 11 78.9 +/- 4.5 12.9 +/- 1.2
Njet=1 ee+mm 140 18.0 +/- 5.2 111.3 +/- 8.6 39.8 +/- 5.4 40.4 +/- 3.1 21.2 +/- 5.4
• ATLAS has less signals and less backgrounds than CMS.• Njet=0: signal (97 vs 146), backgrounds (739 vs 789)• Njet=1: signal (40 vs 60), backgrounds (261 vs 320)
22/28
hWW(*)lnln: mT distributions • Different flavor results are shown. • Data well agree with the expectation including 125 GeV Higgs signals.
Njet=0
ATLAS
CMS
Njet=1 Njet>=2
• For the VBF analysis• mjj>500 GeV• |Dyjj|>2.8• No jets (pT>20 GeV) in rapidity gap• Require both lepton in rapidity gap
23/28
hWW(*)lnln: significance• ATLAS– Combined: 3.8s observed (3.7s expected) at mH=125 GeV
– VBF: 2.5s observed (1.6s expected) at mH=125 GeV• CMS– Shape-based: 4.0s observed (5.1s expected) at mH=125 GeV
– Cut-based: 2.0s observed (2.7s expected) at mH=125 GeV• Shape-based analysis largely improves sensitivity.
ATLASCMS
24/28
hWW(*)lnln: signal strength (=sobs/sSM)
• ATLAS (for mH=125 GeV)
• CMS (for mH=125 GeV)
• All values are consistent with 1 (=the SM expectation).
ATLAS CMS
79.01.66(syst.)42.0(stat.)67.066.136.00.82(syst.)28.0(stat.)24.082.0
0.311.01(lumi.)04.0.)(expt.syst12.0.)(theo.syst19.0(stat.)21.001.1
V
F
mmm
37.071.0
21.00.76(syst.)16.0(stat.)13.076.0
based-cut
based-shape
m
m
When mF (mV) is evaluated, mV (mF) is profiled and constrained mainly by Njet<=1 (Njet>=2) signal region.
25/28
hWW(*)lnln: spin• Minimal graviton-like spin-2 model (2+
m) hypothesis is tested against the SM (0+) hypothesis.
• 2+m hypothesis is disfavored at CLS=1% to 14% by ATLAS and CMS.
fqqbar CLs
0% 5%25% 3%50% 2%75% 1%
100% 1%
fqqbar CLs
0% 14%
ATLAS• Varied qqbarX and ggX
fractions.• Boosted Decision Trees with
mll, pTll, Dfll and mT.
CMS• Consider ggX process only.• Maximum likelihood fit using
2D (mT-mll) templates
26/28
Conclusions
• ZZ(*) and WW(*) final states are excellent tools for Higgs Physics at the LHC.
• Statistical significance of the new boson around 125 GeV gets higher. – ZZ(*): 6.6s (ATLAS 124.3 GeV), 6.7s (CMS 125.8 GeV)– WW(*): 3.8s (ATLAS 125 GeV), 4.0s (CMS 125 GeV)
• Its mass is determined with <1 GeV uncertainty by each experiment.
• Its signal strengths, spin and parity are almost consistent with those of Standard Model Higgs boson.
27/28
References• hZZ(*) decay mode
– hZZ(*)4l • ATLAS-CONF-2013-013, CMS-PAS-HIG-13-002
– hZZllnn • ATLAS arXiv:1205.6744, CMS-PAS-HIG-13-014
– hZZ(*)llqq • ATLAS arXiv:1206.2443, ATLAS-CONF-2012-163
• hWW(*) decay mode– hWW(*)ln ln
• ATLAS-CONF-2013-030, ATLAS-CONF-2013-031, CMS-PAS-HIG-13-003– hWWlnqq
• ATLAS arXiv:1206.6074, CMS-PAS-HIG-13-008– WhWWW(*)ln ln ln
• ATLAS-CONF-2012-078, CMS-PAS-HIG-13-009– 2HDM HWW(*)enm n
• ATLAS-CONF-2013-027 https://twiki.cern.ch/twiki/bin/view/AtlasPublic/HiggsPublicResultshttps://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsHIG
28/28
Backup slides
Backup
29/28
Programhttp://www.ilc.tohoku.ac.jp/higgsandbeyond2013/?page_id=10
== 5th June ==2. Overview
– Theoretical Introduction – Michael Dine (University of California, Santa Cruz)– Higgs physics Theoretical Overview – tbc– LHC accelerator status and plan before HL-LHC – Frank Zimmermann (CERN)– Summary of Higgs and BSM physics at ATLAS – Francesco Conventi (University of Napoli)– Summary of Higgs and BSM physics at CMS - Serguei Ganjour (DSM/DAPNIA, CEA/Saclay)
3. Higgs at the LHC– h –> ZZ, WW – Susumu Oda (Kyushu University)– h –> gamma gamma Matteo Sani (University of California, San Diego)– h –> tautau, mumu – Harald Fox (Lancaster University)– h –> bb – Tristan Arnoldus Du Pree (University Catholique de Louvain)
[Banquet]== 6th June ==3. Higgs at the LHC
– tth – Michele Pinamonti (INFN Udine and SISSA Trieste)– Combined analysis : mass, width, J^PC, coupling – Alessio Bonato (CERN)
30/28
Trigger ET/pT thresholds in 2012
ZZ* WW*
single double triple single double
ATLAS 25 (e)24 (m)
12/12 (e)12 (e)/ 8 (m)24 (e)/ 8 (m)13/13 (m)18/8 (m)
24 (e and m)
CMS 17/8 (e and m) 15/8/5 (e) ? (e and m) ? (e and m)
ATLAS-CONF-2013-013, page 4ATLAS-CONF-2013-030, page 1CMS-PAS-HIG-13-002, page 4CMS-PAS-HIG-13-003, page 2
CMS (ZZ*): e>98%
CMS (WW*) ee: e~98%, mm: e~97% em: e~96%
ATLAS (ZZ*) 4e: e~100% 4m: e>97%
ATLAS (WW*) single-e: e~90%, single-m (|h|<1.05): e~70% single-m (1.05<|h|<2.4): e~90%
31/28
ATLAS resonance plots 32/28
CMS resonance plots 33/28
hZZ(*)4l: CMS discriminant variables 34/28
hZZ(*)4l: signal strength and massATLAS CMS
5040
5.03.0
6.05.0
71
GeV (syst)(stat)3.124..
H
.μ
m
30.024.091.0
GeV 0.2(syst)(stat)5.08.125
mHm
35/28
hZZ(*)4l: massATLAS CMS
36/28
Phys. Rev. D 81, 075022 (2010) 37/28
hZZ(*)4l: spin and parity
ATLAS• 0+ vs 2+
m
CMS
(95%C.L.) 58.000.0 23.0
00.0
23
21
23
3
AA
Afa
38/28
MC simulation (ATLAS)Process MC generatorggF POWHEG+PYTHIA8
VBF POWHEG+PYTHIA8
VH, ttH PYTHIA8
gg, qqH(alternative JP) JHU+PYTHIA8
qq, gqWW POWHEG+PYTHIA6
qq, gqWW+2j Sherpa with no O(as) terms
ZZ(*)qq Sherpa
ggWW GG2WW+HERWIG
ggZZ gg2ZZ
tt MC@NLO+HERWIG
Single top: tW, tb MC@NLO+HERWIG
Single top: tqb Acer MC+PYTHIA6
Drell-Yan Z/g*, inclusive ALPGEN+HERWIG
Z(*)ll+2j Sherpa process up O(as)
Z(*)Z(*)4l POWHEG+PYTHIA8
WZ/Wg*, mZ/g*>7 GeV POWHEG+PYTHIA8 (WW), PYTHIA (ZZ)
Wg*, mg*<7 GeV MadGraph+PYTHIA6
Wg ALPGEN+HERWIG
Parton showering (PYTHIA8), hadronization(PYTHIA8), underlying event (PYTHIA8) orParton showering (HERWIG), hadronization(HERWIG), underlying event (JIMMY)CT10 PDF for POWHEG, MC@NLOCTEQ6L1 PDF for ALPGEN, MadGraph, PYTHIA6, PYTHIA8, JHU
39/28
MC simulation (CMS)Process MC generatorggF POWHEG+PYTHIA6
VBF POWHEG+PYTHIA6
VH, ttH PYTHIA6
gg, qqH(alternative JP) JHU+PYTHIA6
qqWW MadGraph+PYTHIA6
ggWW GG2WW+PYTHIA6
ggZZ gg2ZZ+PYTHIA6
tt POWHEG+PYTHIA6
Single top: tW POWHEG+PYTHIA6
Drell-Yan Z/g*, inclusive MadGraph+PYTHIA6
W+jets MadGraph+PYTHIA6
Z(*)Z(*)4l POWHEG+PYTHIA6
WZ MadGraph+PYTHIA6
CT10 PDF for POWHEGCTEQ6L PDF for MadGraph, PYTHIA6, JHU
40/28